Effect of local chemistry on microstructural stability and local deformation mechanisms in relation to hydrogen embrittlement of Fe base fcc alloys

具有面心立方晶体结构的工业铁基合金的氢脆是几十年来一直被广泛研究的话题。其原因是这一主题具有很高的技术相关性。由于最近关于可再生能源和使用氢气储存能源的讨论，它变得更加重要。关于金属的脆化机制，文献中主要讨论了三种理论，即氢致脱粘、金属氢化物的形成和氢增强局域塑性的HELP机制。对于某些通常是标准化的合金，氢脆的机理是已知的。然而，对于奥氏体钢，仍然缺乏将氢存在下的宏观性能与显微组织性能联系起来的信息，后者是这些高合金化材料生产和加工的结果。出版的作品经常使用众所周知的标准化材料，而不考虑程序和热机械历史。研究项目的目的是为填补这一知识空白做出贡献。为此，应研究铁基合金的预定义模型系统，以了解偏析导致的合金元素的凝固和分布情况。基于CALPHAD和相场法的模拟将与WDS和EDS测量一起应用。用空间分辨衍射法(EBSD)研究了在外氢存在和不存在的情况下的局部变形和破坏机制。该研究项目的总体目标是预测当地的化学成分，并从中得出当地材料的性质(如相稳定性、层错能)。最后，这些信息应与控制材料宏观性质的氢的局部影响相关联。

Hydrogen embrittlement of technical Fe base alloys with face centered cubic crystal structure is a topic that has been intensively investigated for decades. The reason for that is the high technical relevance of this topic. It gains even more importance due to the recent discussion on renewable energy sources and the use of hydrogen for energy storage. Concerning embrittlement mechanisms of metals, mainly three theories are discussed in literature, namely the hydrogen induced decohesion, the formation of metal hydrides, and the HELP mechanism (hydrogen enhanced localized plasticity). For certain, usually standardized, alloys, the mechanisms of hydrogen embrittlement are known. However, for austenitic steels there is still a lack of information to relate the macroscopic properties in the presence of hydrogen with microstructural properties, the latter being a result of production and processing of these high-alloyed materials. Published works often makes use of well-known and standardized materials without considering the procedural and thermomechanical history. The objective of the research project is to make a contribution to fill this gap of knowledge. To do so, pre-defined model systems of iron based alloys shall be investigated with respect to solidification and distribution of alloying elements being a result of segregation. Simulations on the basis of the CALPHAD and the phase field method will be applied along with WDS- and EDS-measurements. Investigations of the local deformation and failure mechanisms with and without the presence of external hydrogen will be performed ex-situ by space-resolved diffraction methods (EBSD). The overall aim of the research project is the prediction of local chemical compositions and to derive local materials properties (e.g. phase stability, stacking fault energy) from that. Finally, this information shall be correlated with the local influence of hydrogen that controls the macroscopic properties of the material.